Who writes the test plans in your shop? Who should write them?

I realize developers (like me) regularly do their own unit testing whilst developing and in some cases even their own Q/A depending on the size of the shop and the nature of the business, but in a big software shop with a full development team and Q/A team, who should be writing those official "my changes are done now" test plans?

Soon, we'll be bringing on another Q/A member to our development team. My question is, going forward, is it a good practice to get your developers to write their own test plans?

Something tells me that part of that might make sense but another part might not...

What I like about that:

• Developer is very familiar with the changes made, thus it's easy to produce a document...

What I don't like about that:

• Developer knows how it's supposed to work and might write a test plan that caters to this without knowing it.

So, with the above in mind, what is the general stance on this topic? I'm of course already reading books like the Mythical Man-Month, Code Complete and a few others which really do help, but I'd like to get some input from the group as well.